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Green walls

With gardens becoming smaller, making use of every surface makes sense and can look striking. Many types of plants will tolerate the high life in a green wall, from herbs and fruit to grasses and ferns. Whether in sun or shade, covering walls with plants can enhance the smallest of spaces.

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Introduction

providing the building with an extra layer of insulation, so cutting down on energy loss and decreasing in heating requirements, even in modern, well-insulated homes

helping to keep homes cool in summer. Unlike brick and concrete walls, green surfaces don’t store up the sun’s energy in the daytime and release it as night-time in the same way

offering great aesthetic benefits

providing habitats for insects

contributing to improvement of urban air quality

contributing to reduced noise pollution

Types of green walls

At their most simple, green walls can just be a planting of wall shrubs and climbers (direct greening). It’s a claddings made from plants such as pyracantha or ceanothus can provide many of the benefits offered by more complex systems.

At the other extreme are engineered, planting systems (indirect greening and living wall systems). These often consist of modules fixed against a wall that contain soil or media for the plants to grow in. These often require irrigation systems and may need professional installation and maintenance.

To be more precise, the types of green wall have been categorised as:

Direct greening is a system where a self-attaching climber utilises the substrate of the façade for support and, sometimes, nutrition.

Indirect greening includes some form of engineered solution, from trellises to wires for the climbers to use; thus providing a gap of insulating air between the building and the plant.

Living wall systems (LWS), finally, are constructed with planter boxes or felt; these do not require the plants to be climbing, they often need to be irrigated and plants for intensive green roofs are frequently suitable for these systems.

Indirect greening: This is within the skills of most competent DIYers and requires the surface to be first clad with wires or trellis. Climbing plants are then grown against it

Living wall systems: For smaller budgets, there are simple grow-bag-type products for walls or you can plant up one or more small panels that can be added to, depending on space and budget. These are available from garden centres. Introduce the plants at as small size as possible, ideally as plugs. Establishment is likely to be more successful at this stage of development

Higher cost, professional installations

Indirect greening: Large scale installations of wire, trellis or supports, such as covering the side of a house. It is the scale that makes this more expensive and for professional installation.

Living wall systems: can use plants grown in cells containing compost or other growing media, which are connected to drip irrigation. Harvested rainwater can be used with some systems. These are installed by specialist companies. Green walls can be installed indoors with additional artificial lighting

Choosing plants

If the wall you are about to add plants to receives less than half a day of sun in mid-summer, choose plants for shade

To simplify planting and watering needs, try to choose plants that have similar light and moisture requirements to the conditions on offer

When to plant green walls

Spring is the best time to plant because plants are coming into active growth and will establish quickly.

Further reading

Planting Green Roofs and Living Walls by N Dunnett & N Kingsbury (Timber Press, 2004 ISBN-9780881929119). This book is made available through the RHS Lindley Library.

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Pyracantha can be used to create a green wall simply by planting one against it and training the stems on wires.

Suitable plants

There is a broad range of plants available to clothe walls, and includes the following:

Climbers and wall shrubs are the simplest way of adding interest to walls. There will be a climber to suit your wall, whether in sun or shade

In green wall systems, a range of herbaceous perennials, grasses, herbs, fruit and vegetables can be planted

Plants for summer interest (sold as annuals, patio plants or bedding perform well and are widely available as plugs in spring. Alternatively, grow plants from seed. Experimentation with different plants is also worthwhile